You are testing the hypothesis that the coefficients for the dummies
are equal in magnitude but opposite in sign. Are you sure that is
what you want, as opposed to just testing that both coefficients equal 0, e.g.

test D1 D2
This will work with mi test.
But, if you really want to test your hypothesis as stated, see
help mi test
It includes examples for more complicated forms of hypotheses.
At 10:09 AM 5/27/2013, Eduardo Moreira wrote:

Dear all,

I am sorry if this has been asked before, but I searched and
couldn't find the answer to this question.

Say you want to compare 2 regression models on the same dependent
variable Y. The second model contains 2 dummy variables, D1 and D2.